class DataTable {

    public columns: Array<string> = new Array();

    public rows: Array<DataRow> = new Array();
}

class DataRow {

    public cells: Array<string> | undefined;
}

class Test {

    public jsonObject =
    {
        "columns": ["ColumnA", "ColumnB", "ColumnC"],
        "rows":
        [
            { "cells": ["A1", "B1", "C1"] },
            { "cells": ["A2", "B2", "C2"] }
        ]
    };

    public run() {
        // var x = (<DataTable>this.jsonObject);
        // x.columns.push("ColumnD");
        // console.log(x.columns.length);
        console.log( "aaaaaaaa");
        console.log( "03");
    }
}

var test = new Test();
test.run();